Solicitor-General Justin Gleeson SC told the court when it came to genuine science "killing the subject you are studying in order to learn more about it ... should be a matter of last resort not the first or default option".

"Japan can not seek to authorise the killing of hundreds of whales year on year, indefinitely, and yet claim to be acting within a special power for limited purposes," the solicitor-general told the 16-judge panel.

Mr Gleeson said whale meat was still being supplied to the Japanese market in a business-like operation just as it was prior to Tokyo agreeing in 1986 to the ban on commercial whaling.

Clashes between Japan's whaling fleet and Sea Shepherd activists have become a dramatic staple of the southern hemisphere summer in recent years.

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